Prior art devices or apparatus have been developed for cleaning carpets, other floor coverings, upholstery, and the like, by utilizing a pump for spraying a hot cleaning solution onto the carpet fibers and, following a very short time interval, extracting the soiled cleaning solution and the soil components through a suction nozzle to a wet pick-up vacuum cleaner. The cleaning solution utilized in these devices or apparatus are generally of the type that may be called detergent solutions and comprise various surfactant agents, optical brighteners, antifoam agents, and the like dispersed in a hot water solution. In addition, builders, softening agents, organic solvents and other cleaning compounds may occasionally be included. Such devices or apparatus have come to be called hot water or steam extraction cleaning apparatus although seldom is live steam actually employed.
However, because such floor covering and other materials can be permanently discolored or otherwise injured by excessive absorption of moisture, it is desirable that the cleaning solution remain in contact with the fibers for a minimal period of time. In order to enable the many compounds to do an effective cleaning job in the short interval of time allowed, it is desirable that the cleaning solution be applied while quite hot.
Such hot water or steam extraction type carpet upholstery cleaning machines have heretofore been generally separable into two distinct types or classes: commercial units which are characterized by substantial size, weight, and energy requirements, and low cost residential or home type units which are characterized by high portability, lesser size, energy requirements and weight, and generally, lower cost. While commercial type devices or apparatus have been heretofore provided with heating means for heating the cleaning solutions utilized, such home use or residential devices or appliances as have been heretofore available have not included provision for heating the cleaning solution. Instead, the household water system has been relied upon for providing sufficiently hot water for the cleaning solution and a relatively short cycle time, during which the water is expected to remain sufficiently hot.